 # RACING MATH FORMULA'S UNDER CONSTRUCTION COME BACK SOON

• 1
• 2
• 3

My Favorite Web sites

## BACK TO MAINPAGE

```CAR MATH FORMULA'S
Here are the formulas for most of the Car Math Calculators used on this site as well as a few additional ones that are not on the site.
NOTES
N1) Many of the formulas use the value of pi which is 3.1415927
N2) Some formulas contain notation such as ^2 which means "squared"

Formulas for displacement, bore and stroke
pi/4 = 0.7853982
cylinder volume = pi/4 x bore^2 x stroke
stroke = displacement / (pi/4 x bore^2 x number of cylinder.

Formulas for compression ratio
(CylVolume + ChamberVolume) / ChamberVolume
cylinder volume = pi/4 x bore^2 x stroke
chamber volume = cylinder volume / compression ratio - 1.0
displacement ratio = cylinder volume / chamber volume
amount to mill = (new disp. ratio - old disp. ratio / new disp. ratio x old disp. ratio) x stroke

Formulas for piston speed
piston speed in fpm = stroke in inches x rpm / 6
rpm = piston speed in fpm x 6 / stroke in inches

Formulas for brake horsepower
horsepower = rpm x torque / 5252
torque = 5252 x horsepower / rpm
brake specific fuel consumption = fuel pounds per hour / brake horsepower
bhp loss = elevation in feet / 1000 x 0.03 x bhp at sea level

Formulas for indicated horsepower & torque
horsepower = mep x displcement x rpm / 792,00
torque = mep x displacement / 150.8
mep = hp x 792,000 / displacement x rpm
mep = hp x 792,000 / displacement x rpm
mechanical efficiency = brake output / indocated output x 100
friction output = indicated output - brake output
taxable horsepower = bore2 x cylinders / 2.5

Formulas for air capacity & volumetric efficiency
theoretical cfm = rpm x displacement / 3456
volumetric efficiency = acutal cfm / theoretical cfm x 100
street carb cfm = rpm x displacement / 3456 x 0.85
racin carb cfm = rpm x displacement / 3456 x 1.1

Formulas for tire size & their effect
tire diameter = 2 x selection width x aspect ratio / 2540 + rim diameter
effective ratio = old tire diameter / new tire diameter x original ratio
actual mph = new tire diameter / old tire diameter x actual mph

Formulas for g force & weight transfer
drive wheel torque = flywheel torque x first gear x final drive x 0.85
wheel thrust = drive wheel torque / rolling radius
g = wheel thrust / weight
weight transfer = weight x cg height / wheelbase x g
lateral acceleration = 1.227 x raduis / time^2
lateral weight transfer = weight x cg height / wheel track x g
centrufugal force = weight x g Formulas for shift points
rpm after shift = ratio shift into / ratio shift from x rpm before shift
drivehsaft torque = flywheel torque x transmission ratio

Formula for instrument error
actual mph = 3600 / seconds per mile
speedo error percent = difference between actual and indicated speed / actual speed x 100
indicated distance = odometer reading at finish - odometer reading at start
odo error percent = difference between actual and indicated distances / actual distance x 100

Formulas for MPH RPM gears & tires
mph = rpm x tire diameter / gear ratio x 336
rpm = mph x gear ratio x 336 / tire daimeter
gear ratio = rpm x tire diameter / mph x 336
tire diameter = mph x gear ratio x 336 / rpm

Formulas for weight distribution
percent of weight on wheels = weight on wheels / overweight x 100
increased weight on wheels = [ distance of cg from wheels / wheelbase x weight ] + weight

Formulas for center of gravity
cj location behind front wheels = rear wheel weights / overall weight x wheelbase
cg location off-center to heavy side = track / 2 - [ weight on light side / overall weight ] x track
cg height = [ level wheelbase x raised wheelbase x added weight on scale / distance raised ] x overall weight ```